The individual reactions involved in the assembly of the oligosaccharide chain of aorta glycoproteins are currently under investigation. This assembly mechanism involves participation of lipid-linked oligosaccharide intermediates and takes place on membrane fractions isolated from the intimal layer of pig aorta. These membrane fractions catalyze the incorporation of man from GDP-man and GlcNAc from UDP-GlcNAc into a series of oligosaccharides linked to lipid through a pyrophosphoryl linkage. At least 8 different oligosaccharides have been separated after mild acid hydrolysis of the lipid linked oligosaccharides and these oligosaccharides are being studied by various chemical methods to determine their structures. We are also studying the individual steps in assembly of the lipid intermediates. The mannosyl transferase which forms mannosyl-phosphoryl-polyprenol and the GlcNAc transferase which makes GlcNAc-pyrophosphoryl-polyprenol have been solubilized by treatment of membrane fractions with Triton X-100 and these two enzymes have been partially purified on DEAE-cellulose. The properties of these enzymes are now being studied. We are also solubilizing the mannosyl transferase which adds mannose to produce the man-GlcNAc-GlcNAc-pyrophosphoryl-polyprenol. Other studies underway involve transfer of mannose from mannosyl-phosphoryl-polyprenol to lipid-linked oligosaccharides and from lipid-linked oligosaccharides to protein. BIBLIOGRAPHIC REFERENCES: Forsee, W. T. and Elbein, A. D. (1976). Biosynthesis of Lipid-Linked Oligosaccharides and Glycoproteins in Aorta. Stimulation by Acceptor Lipids Isolated from Aorta. Proc. Natl. Acad. Sci. 73, 2574-2578. Adya, S. and Elbein, A. D. (1976). Purification and Properties of alpha-Galactosidase from Aspergillus niger. J. Bacteriol., in press.